1. Field of the Invention
The invention relates to a vehicle assist system; and more specifically, to a system providing a hill start assist with an enhanced response behavior.
2. Description of Related Art
Starting on an upward gradient presents something of a challenge to the driver with conventional motor vehicles, in particular in motor vehicles with a manual transmission. When starting, the driver must coordinate releasing the brake with engaging the clutch and pressing the accelerator so the vehicle ideally moves from the braked state directly to the driven state without the vehicle rolling back. But in reality, even a highly skilled driver cannot always prevent rolling back with a steep upward gradient. In order to counter these problems, a hill start aid/assist was developed whereby on an upward gradient, even after the brake pedal is released, the vehicle brake releases only when the engine provides enough torque to prevent the vehicle from rolling back. The presence of an upward gradient is normally established with an inclination sensor, the hill start aid/assist being automatically activated at a certain threshold value (for example a 1% to 3% upward gradient).
While in principle these systems operate reliably and have proven effective, problems can arise when the vehicle comes to a stop, for example, in a depression, with the front wheels on the rising edge of the depression while the rear wheels are on a flat surface. Here the inclination of the vehicle under certain circumstances is extremely low, or even zero, and the hill start aid/assist will not be activated even though there may be a local upward gradient of considerable magnitude (for example 5 or 10%) in the region of the front wheels. When an attempt to start is made, this local upward gradient may cause the vehicle rolling back, this potentially leading to a collision with a vehicle at the rear or even with a pedestrian.
Although there are also systems where the driver can manually switch on the hill start aid/assist as required, this requires additional attention of the driver and the driver either does not notice local upward gradients or finds it difficult to estimate the position of the axles in relation to the local upward gradient since the axles are not in view.